The disclosure risks fuelling concerns that the party’s high command engaged in a cover up instead of acting properly over the allegations against the peer, who was one of the most powerful Liberal Democrat figures at the time.

Lord Rennard has denied claims that he inappropriately touched a number of women who were working for the party.

Mr Clegg made the disclosure after Cathy Newman, the Channel 4 News journalist who broke the story last week, called the show and asked directly whether Lord Rennard’s behaviour “was part of the reason he went”.

The Deputy Prime Minister has appeared frustrated with journalists pursuing the story, and on Tuesday attacked the “self-appointed detectives” in the media for investigating the claims against Lord Rennard.

However, on LBC's weekly "Call Clegg" slot, he praised Ms Newman’s “excellent piece of investigative journalism” which brought the allegations to light and insisted that he supported a free media.

Mr Clegg is under pressure to explain exactly what he knew about the allegations, when he was first told of the concerns, and what he did to address them.

Sandra Gidley, a former Lib Dem MP, told the Telegraph she had warned Mr Clegg about Lord Rennard’s alleged behaviour after 2007, after he became party leader.

Mr Clegg said he believed he had first been told in 2008 but accepted that he could not remember the “precise date”.

“I can only tell you the truth as I can recollect it now. All I can recollect is that in 2008, the year after I became leader, the general concerns expressed to me and my office were such that we acted upon them.”

He continued: “My recollection is that 2008 is the year in which the concerns were brought to my attention.

“You ask me for the precise date of a conversation which took place, according to Sandra, six years ago. As Sandra has said, the conversation was of a general nature. I think she said in the lobby of the House of Commons.

“I don’t even know whether it was before or after I was leader. Of course I need to look into all of these things.”

Mr Clegg was criticised by callers to the phone-in show over his handling of the allegations.

One caller, named only as Mary, said: “You were asked a question. You waffled on for 10 minutes without answering, so I ask you again, why did you not have an inquiry when you found out about this five years ago?”

The Deputy Prime Minister insisted he had given “the full candid answer that I can”, and that he had acted on the claims when they first emerged.

The party launched inquiries into the claims last week.

Mr Clegg told LBC listeners: “Of course I’m keen that these investigations should look at everything with hindsight but we acted and acted as we could with what we were told at the time.

“The women have been let down. There have been some serious mistakes.”

He said he and his party “have got nothing to hide”.

“All I care about at the end of the day is that my party, the Liberal Democrats, a party which believes to its core in treating people with dignity and respect, does so itself. That clearly did not happen. That is a very serious issue.

“It distresses me immensely that women who I know, who are really good people, who I respect and admire a lot, feel as abandoned as they clearly felt they were.”

Lord Rennard, who stepped down as chief executive on health grounds in 2009, has said he is ready to "co-operate with any properly-constituted inquiry" into allegations of inappropriate behaviour.

The peer issued a strenuous fresh denial of any wrong-doing as senior Liberal Democrats met Metropolitan Police officers to discuss the case.

Scotland Yard said the meeting was held to help ascertain whether any criminal activity had taken place, adding: "That work continues."